Plating of cadmium



K6 few/4170128 8 Nov. 2, 1937.

flmke faldoreswnw PLATING OF CADMIUM Filed Oct. 17, 1935 Acetaldehyde l Aldol Crotonaldehyde Aldacets I I x I l l l l l l v l I i Paraldol i f 'l l """1 l' '"l Alkalin 'T" Solution L -J i 1 Q) Amog Amo Gyamdereaction Amulducegs H reaction reaction Product Product 5 Product I 1 I I *l Hydrogenation Hydrogenation Hydrogenation l I l I L l N-Containing Reduced Amoreaction Product N-Containing Reduced Cyanide- Reaction Product N-Containing Reduced Ame-reaction Product INVENTOR.

GEORGE LUTZ.

ATTORNEY.

cadmium plate on a flat cathode with a bath Patented Nov. 2, 19 37 UNlTED STATES name or CADMIUM George Lutz, Rocky River, Ohio, assignor, by

mesne RS8 poration of Delaware Application October 17,

17 Claims.

This invention relates to the eleotrodeposition of cadmium from cyanide-cadmium baths, andis particularly directed to cyanide-cadmium plating compositions, plating baths, and plating processes which employ, as an addition agent, a reduced amketaldoresin whereby a bright, smooth, uniform cadmium deposit is obtained.

It has heretofore been proposed to modify the character of cadmium deposits by the use of organic addition agents such as sulflte cellulose waste, dextrin, starch, alkylated naphthalene sulfonic acids, wool, cafleine, shellac casein, licorice, glucose, alkali reaction productsof heterocycllc aldehydes, furfural, gum arabic, and. gelatine."

It,.'has been necessary to employ an addition agent and/or a brightener with cyanide-cadmium plating baths, because, without such modifying agents, cadmium deposits of, exceedingly poor character and appearance are obtained. The properties of electrodeposited cadmium are largely determined by the addition agent. and/or brightener used, and the desirability of a cad mium plate is, to a great extent, dependent upon the eflicacy of the modifying agents employed.

The properties of a cadmium plate are partly dependent, in commercial practice, upon certain characteristics of the plating bath employed,

and these characteristics can be modified, to] some extent, by suitable organic addition agents and/or brighteners. Under strictly controlled conditions, one can deposit a fairly satisfactory which, in ordinary commercial practice, would be unsatisfactory. Under the usual conditions of commercial operation, particularly when recessed articles or articles of irregular shape are to be plated, a bath must have a fairly wide bright current density range and good throwing power if even moderately satisfactory results are to be obtained. The throwing power and the extent of from cyanide-cadmium baths as a bright, smooth,

lustrous, ductile, adherent deposit. Baths containing these novel addition agents are characterized by good throwing power and by a wide bright current density range.

In the accompanying drawing there are shown ignments, to E. I. du Pont de Nemours & Company, W

n, Del., a con 1935, Serial no. 45,426

the relationships existing between various derivatives which constitute the addition agents of my invention, and there are also shown, diagrammatically, the methods of preparation of the various derivatives.

Represented by a circle in the upper left-hand corner of the drawing are the starting materials from which my addition agents are derived. .The starting materials are designated ketaldones but, as will be explained below, certain ketaldones are particularlysuitable for my purpose.

Mypreferred starting materials are, generally speaking, aliphatic and carbocyclic ketaldones, that is aldehydes and ketones, but, as will become apparent hereinafter, the best results are obtained by the use of certain aliphatic and carbocyclic aldehydes and ketones.

The term ketaldonyl has been applied to designate the 0 0 group as it appears in aldehydes and ketones in contradistinction to the 0:0 group as it appears in acids. Of course, th carbonyl group as it appears in acids,

is very difierent in its propertiesfrom the car bonyl group as it appears in aldehydes and keas used herein designates a carbonyl group in which a third carbon valence is joined to carbon and in which the remaining valence is satisfied by carbon or byhydrogen. Or, in chemical symbols, the ketaldonyl group as used herein is of the type tones, and the expression "ketaldonyl group is wherein R is a hydrocarbon radical and wherein R is hydrogen, in the case of an aldehyde, or R is a hydrocarbon radical, in the case of a ketone. It will also be understood that the ketones and aldehydes themselves are referred to herein as ketaldones in accordance with this terminology.

The starting materials which I employ are, broadly, 'ketaldones. While I may use aldoses, ketoses, heterocyclic aldehydes and ketones or any other such ketaldones, I prefer. to use allphatic and carbocyclic ketaidones which do not contain a carboxyl group, which do not contain sulfur, and which do not contain nitrogen. The starting materials, moreover, should contain no more than two hydroxyl groups and preferably should contain at least two carbon atoms. More specifically, I prefer to employ ketaldones which contain only carbon, hydrogen, and oxygen, which contain at least two carbon atoms, and in which the hydrogen-oxygen ratio is greater-than that of water.

As is illustrated inthe drawing, the starting materials, the ketaldones, are reacted with ammonia or an amine, in alkaline solution, to produce an amo-reaction product. It will be observed that amo is used to designate both ammonia and-an amine. As will'be noted hereinafter, the amo-reaction products of the ketaldones are very similar in their physical and chemical characteristics. They all contain nitrogen, and all are, apparently, complex mixtures. I have,

accordingly, designated these reaction products amketaldoresins. The nature of the products and the nature of the reaction will be discussed in more detail hereinafter.

The amketaldoresins are subsequently modified by hydrogenation to yield nitrogen-containing derivatives which are effective as addition agents. These derivatives, while more effective, are very similar to the amketaldoresins, ordinarily differing slightly as to color and solubility.

A preferred group of ketaldones, the aldacets, are illustrated in the upper right-hand corner of the drawing. More will be said hereinafter regarding the members of the illustrated aldacet equilibrium. As is shown in the drawing, the aldacets, like the ketaldones generally, are reacted with ammonia, or cyanide to produce an amketaldoresin. The particular amketaldoresln produced from the aldacets are designated herein, the amaldacets."

' According to my invention, the amaldacets are hydrogenated, as were the amketaldoresins .generally, to produce nitrogen-containing derivatives.

The ketaldones which I employ as starting materials are reacted in weak alkaline solution with an amo to produce an amo-reaction product from which addition agents of my invention may be prepared. As will be noted hereinafter, the use of cyanide is considered substantially equivalent to reacting the ketaldones with amoes in alkaline solution.

The amketaldoresins are preferably derived from the aliphatic ketaldones termed the aldacets. The derivatives of the aldacets are typical of the amketaldoresins, and their preparation will be described below in some detail as illustrative of the amketaldoresins generally.

The aldacets comprise the aliphatic aldehydes: acetaldehyde, aldol, crotonaldehyde, and paraldol. In dilute alkaline solution the aldacets appear to exist in equilibrium, any one of the aldacets leading to the production of all at a rate of conversion apparently depending upon the specific aldacet first present. The aldacet equilibrium is illustrated in the upper, right corner of the drawing.

Referring to the aldacet equilibrium in more detail, it is noted that acetaldehyde in dilute alka line solution is quickly converted to aldol thus:

The aldol may lose one molecule of water and become crotonaldehyde, thus:

H H H H W H an H Etna-al a t: 43:0

The n in Equation 3 is a whole number, probably 2. In order to visualize the relationships existing between the aldacets, reference should be had to the accompanying drawing wherein these relationships are diagrammatically illustrated.- It is to be understood that the relationships are shown with reference to the compounds in dilute alkaline solutions or in alkali metal cyanide solutions.

In the drawing, acetaldehyde is-illustrated as converting to aldol. The aldol may go toparaldol or to crotonaldehyde. The aldol might also go back to acetaldehyde, but only to a small extent. The paraldol may go back to aldol,'or it may lose water and go to crotonaldehyde, though this latter conversion probably takes place to a very small degree. The crotonaldehyde may form from acetaldehyde, aldol, or paraldol, and, by gaining water, may revert to any of them, though it is likely that it would move largely by way of aldol.

As is seen in the drawing, then, we may consider the aldacets as being in equilibrium. This equilibrium will, according to my belief, be substantially the same regardless of which of the four substances are initially added to the cyanide solution, though, as will hereinafter be noted, the aldacets are not entirely equivalent, and it is possible that some of the aldacets in dilute alkaline solution form this aldacet equilibrium rather slowly or move more rapidly in certain directions than in others.

While I have mentioned only acetaldehyde, aldol, crotonaldehyde, and paraldol as members of this sub-genus, I may use any condensation product of acetaldehyde in dilute alkali solution. Another aldacet is paraldehyde. Ordinarily paraldehyde is considered as forming only in acid solution, but I have reason to believe that at least some paraldehyde forms in the discussed aldacet equilibrium. Paraldehyde is apparently very slow toconvertto other aldacets and probably because of this fact is none too satisfactory as a starting material.

Aldol, acetaldehyde, crotonaldehyde, and paraldol are the only commercially available aldacets at the present time. For practical reasons, therefore, I prefer to use as a starting material an aldehyde selected from the group consisting of acetaldehyde, aldol, crotonaldehyde, and paraldol.

It is to be noted that the aldacets are those aliphatic ketaldones, such as acetaldehyde, aldol, crotonaldehyde, and paraldol, which exist in some sort of equilibrium when one of the said kctaldones is put into alkaline or alkali metal cyanide solution. Generally, then, one might say that the aldacets are aliphatic aldehydes from the group consisting of acetaldehyde and its condensation or equilibrium products in alkaline and alkali metal cyanide solutions.

As a definition for the purposes of this application, then, the aldacets are reversible equilibriumcondensation products of acetaldehyde in alkaline solution and particularly in alkaline solutions such as those of the following Examples I and X.

As will be noted in detail hereinafter, the

aldacets are not entirely equivalent for my purposes but'are substantially so. crotonaldehyde, for example, seems to lead to slightly lower yields. This may be attributable to the fact that crotonaldehyde is but slowly converted to the necessary form, or to some other now unknown cause.

As is above indicated, there is considerable uncertainty as to the extent and nature of the conversion of some aldacets to others. All of the evidence now available to me substantiates the putative theory above advanced as to the nature of the aldacet equilibrium, but it will be understood that direct experimental evidence is obtainable only with great dlfliculty. In most I instances the aldacet equilibrium exists for only a short time, some further action quickly taking place to form resins. That the aldacets are in some kind of equilibrium is relatively certain, but the proportions of individual aldacets and the rates of conversion have, to date, defied exact determination.

It is clearly to be understood that the above description of the relations between the initial materials is for purposes of illustration and that I do not intend to be limited in any way thereby, because the chemistry of these compounds is intricate and obscure, and because my results are obtained entirely apart from theoretical considerations. It is also tob understood that while I refer to aldol, acetaldehyde, crotonaldehyde, and paraldol as resulting from the condensation of acetaldehyde in alkaline solutions, I do not wish to be limited thereby, as I may use aldol, acetaldehyde, crotonaldehyde, and paraldol which have been made in any manner.

Turning now to a consideration of the amketaldoresins produced from the aldacets, it is first noted that the specific amketaldoresins produced by the reaction of the aldacets with amoes or cyanide in alkaline solutions are termed amaldacets." The amaldacets are almost indistinguishable from one another in physical and chemical properties though, as will be noted hereinafter, they differ slightly from one another as to their efficiency as addition agents for cyanidecadmium plating.

It is to be notedthat the term reaction? is used to express whatever occurs when the ketaldones, or specifically-the aldacets, are treated in alkaline solution with cyanide or with an amo. The term reaction is used to distinguish from "condensation as used above with reference to the aldacet equilibrium tho, in fact, the reaction probably includes both polymerizations and condensations.

The amaldacets as well as the amketaldoresins contain nitrogen as determined by the Kjeldahl method. In the amaldacets the nitrogen is present in about the ratio of one nitrogen atom to each two molecules of aldol four of acetaldehyde, one of paraldol, etc.). I have been unable to determine how the nitrogen is located in the amaldacet molecules, and insuflicient evidence is available towarrant any assumptions.

That the amaldacets are not simple compounds, but are complex mixtures, is evidenced by the fact that portions are water-soluble, other portions chloroform-soluble, etc. It seems probable that the amaldacets are the result of many intricate polymerizations, condensations, and reactions.

There may be some condensation products which are not combined with nitrogen, but the fact that a molecular proportion, or an excess, of an amo or of an alkali metal cyanide, to aldehyde give the 'best results, 'leads to the belief that the amount i and ammonium hydroxide were reacted. The reand then react. I conceive of the reaction. as

withdrawing one, or more, of the aldacets from of different paths to produce a number of final products. This is evidenced by the fact that the reaction product is a mixture of separable materials. More is said of this separability hereinafter.

, To illustrate the production of the amaldacets by the reaction of aldacets with ammonia or amines, the following specific examples are given:

Example I Example II A similar amaldacet was produced by reacting 'equimolecular proportions of aldol and monoethanolamine. A product exceedingly similar to the one of Example I was produced. I

Example III One-halt mole of monoethanolamine and one mole of aldol were reacted at temperatures between 30 and 40 C. The product was not as soluble as the product of Example II and, when reduced, it was not as satisfactory an-addition agent for use in cyanide-cadmium plating.

Example IV Equimolecular proportions of aldol and diethanolamine were reacted at room temperatures. A product very similar to those of the above ex-' amples was produced, the productof this example, however, being slightly less soluble than the product of Examples I and II.

Example V Equimolecular proportions of aldol and triethanolamine were reacted at room temperatures. The reaction product of this example was'somewhat less soluble than the products of Examples I and II.

Example VI Aldol was treated with ammonia gas by bubbling the gas through the aldol until no further reaction was noted. The reaction product, when reduced, was rather difilcultly soluble, and was only a moderately eflicient addition agent for cyanide-cadmium plating baths.

Example VII Equimolecular proportions of crotonaldehyde 7 Example VIII Crotonaldehyde and ammonia gas were reacted 75 at about twenty-five degrees centigrade.

example. After a few days the product of this example solidified to a brittle, red resin.

Example IX 1 Acetaldehyde was treated with an excess of gaseous ammonia. An amaldacet similar to that of the preceding example was obtained.

While I have shown the reaction of the aldacets with ammonia, ammonium hydroxide, and with certain amines in the above examples, it will be understood that other amoes may be used. I'may, for instance, prepare the amaldacets by treating the aldacets with amines such as the glucamines, for instance, glucamine and methyl glucamine, or aliphatic amines, for instance, methyl ethylamine, methylamine, and ethylamine.

While the amaldacets may be prepared by conducting the reactions of the above examples at rather widely varied temperatures, I prefer that the reaction be performed at temperatures between about thirty and fifty degrees centigrade. If much lower temperatures be maintained, the reaction products will tend to contain insoluble or relatively inactive constituents. Similarly, the reaction temperatures should not be permitted to rise too high, because, when the reaction proceeds at high temperatures, the reaction product may contain insoluble constituents and may have none too great an eificiency as an addition agent.

It is generally preferred to employ an equimolecular proportion, or an excess, of amine to aldehyde. As will be noted by comparing Examples II and III, less satisfactory amaldacets are produced when less than an equivalent amount of amine is used.

Instead of preparing the amaldacets by the direct reaction of ammonia or amines with the aldacets, they may be prepared by reacting the aldacets with alkali cyanides.

When the, aldacets are treated with liquid hydrocyanic acid, some slight reaction apparently occurs, but the product has but little, if any, activity as an addition agent in cyanide-cadmium plating baths, and hydrogenation according to my invention eifects little improvement. From this fact it appears that when the aldacets are reacted with alkali metal cyanides, no great portion of the reaction product contains the CN" group.

The cyanides are known to hydrolyze to produce ammonia and formates according to the following illustrative reaction:

' It seems possible, accordingly, that the cyanide is more desirable than the reaction products of the aldacets with amoes.

If, as I have assumed, the reaction with cyanide amounts to a reaction with ammonia by reason of the hydrolysis of the cyanide, it is surprising that such a difference in the amaldacets should exist. It seems possible, however, that the differences are attributable to the fact that in an alkali The ,product was very similar to that of the preceding metal cyanide solution the ammonia is somewhat less available. It is possible, of course, that some of the aldacet reacts with the cyanide directly or with some intermediate product of the hydrolysis. It seems probable, however, that the reaction occurs largely between the aldacet and the aminonia produced by hydrolysis of the alkaline cyanide solution.

The following specific examples illustrate the production of the amaldacets by the reaction of aldacets with an alkali metal cyanide.

Example X Five parts, by weight, of technical aldol were added to a solution containing three parts, by

weight, of sodium cyanide in ten parts, by weight,

' the heat of the reaction necessitated a continuous cooling of the reaction mixture to hold the temperature within the desired limits. Later it became necessary to supply heat to the reaction mixture to maintain the temperature. During the reaction a small amount of ammonia was liberated, as was evidenced by the characteristic odor.

The amaldacet-containing reaction mixture obtained may immediately be reduced to form one product of my invention. It is a thick, mobile liquid, dark red in color.

In order to purify and concentrate this reaction product, the solution, after being allowed to cool, was made neutral to litmus with a dilute solution of sulfuric acid. The acid solution consisted of one part by volume of water to one part by volume of concentrated sulfuric acid. There was then added an excess of ten per cent over the volume of dilute acid'required to neutralize the solution. Sodium sulfate was precipitated, and the excess acid used depressed its solubility. The temperature was not allowed to go above 50 C. during this neutralization treatment. Hydrocyanic acid gas was evolved during the treatment and means were provided for disposing of it.

The acid treated solution was allowed to stand for several hours and a dark red fraction rose to the top. This top layer was removed and centrifuged.

The separated top layer, which may be reduced to form apreferred product. of my invention, is a viscous liquid, dark red in color, and it has a specific gravity of about 1.20. At temperatures as low as 17 C. it remains liquid, but at the temperature produced with a freezing mixture of solid carbon dioxide and acetone (below -80 C.) a brittle solid, apparently non-crystalline, is formed. This product is substantially insoluble in such solvents as ether, benzene, and petroleum ether. It is, however, completely soluble in alcohol and acetone.

The products of this example are entirely soluble in cyanide plating baths up to about three grams per liter. One characteristic of both the final product and the reduced, unseparated reaction mixture is that when usedin cyanide cadmium plating baths they exhibit the property of causing a bright deposit of cadmium. This drogenated to produce one product of my incharacteristic serves admirably for the identification of these novel products. i

The amaldacets of this example are not. chemical' compounds, but are mixtures as is evidenced bythe fact that portions of the cyanide reaction products are water-soluble and that smaller portions of the productsare chloroformsoluble. When used as an addition agent in electroplating cadmium, the water-soluble portion of the cyanide reaction products exhibits the property of promoting the formation of a bright finish on recessed parts of an article. The water insoluble portion seems to exercise its major in-.

' stains on the plated article.

The temperature of the reaction ,is relatively important as the yield of the product and its activity as an addition agent seem to be greatly influenced thereby. The activity and, of course,

' the yield of the hydrogenation products of this invention are similarly influenced. The best results seem to be obtained with temperatures between about 45 and 50 C. as used in this example. If lower temperatures are used, there is a decrease in the activity of the product as an addition agent. Below about 30 C. the product rapidly becomes less active with decreases in temperature. If temperatures substantially above 50 areused, the yield of active material is smaller. At about 75 C., for instance,.about one-half of the product is an insoluble resin without much value as an addition agent. Generally, I may use temperatures from about 30 C. to about 75 C., though more specifically I prefer to keep the reaction temperature between about 45 and 50 C.so that 'hydrogenation'products of optimum characteristics may be produced from these materials.

The separation by neutralization with acid was accomplished at 50 C., but rigid temperature control is not necessary. Apparently, as soonas the reaction is complete, the reaction product may be heated to rather high temperatures without substantial damage resulting.

In the examples, sulfuric acid is employed fo removing excess sodium cyanide by converting it to sodium sulfate which then acts tosalt out being less volatile than acetaldehyde and more easily handled than paraldol which is a solid.

As an example of the preparation of an amaldacet from another aldacet, I give the following:

Example XI vention. I

The reaction mixture is preferably concentrated by treatment with dilute sulfuric acid, as

described in Example X. Theproduct issubstantially identical with the concentrated product of Example X described in detail above.

It is noted that in Example x1 a smaller ratio of cyanide to aldehyde was used than in Example X. This seems to lower the yield of active material somewhat. Generally,*the best results are obtained whenthe aldehyde and cyanide are used in substantially molecular proportions, but

.a latitude is permissible.

If less of the alkali metal cyanide be used, the product will be less active, while if an excess of alkali metal cyanide be used, no particular dam'-' age results. When the product is concentrated by neutralizing with dilute sulfuric acid, the excess of cyanide, over that required to form the reaction product, is converted to alkali sulfate and hydrogen cyanide gas, bothof which are separated from the product.

The period of time during which the reaction If the time be too short, the reaction will not be complete and the product will be of low activity when used as an addition agent forcadmium plating, and its hydrogenation product, similarly, will be of low activity. If the time be too long, a product of excellent activity is obtained, but the yield is low. The time of Example XI represents a practical minimum, and I usually prefer to employ a longer period. In general, the reaction temperature should be maintained for not less than about one-half hour, and I prefer to maintain it for not less than about four hours to obtain a product which, when reduced, yields an addition agent of the highest activity.

The following examples illustrate the preparation of products which have a higher ratio of hydrogen to oxygen than have the amketaldoresins, which reduced products constitute addition agents of my invention;

Example XII a To the cyanide reaction product of Example X .was added ten grams per liter of zinc dust. The

zinc dust in the alkaline solution served, of course, as a reducing agent. After the reaction was complete, the solution was treated with sulfuric acid as in.the said Example X to concentrate the resin. Both the reduced cyanide solutionand the concentrated product constitute addition agents for cyanide-cadmium plating. J

. Employing the concentrated product as an addition agent, cyanide-cadmium plating baths were made up as follows:

i Grams per liter Sodium cyanide (NaCN) 130. Cadmium oxide (C(10) 43 Sodium sulfate (Na2SO4) 50 Cobalt sulfate (C0SO4.7H2O) 10 Addition agent 1.2

This bath displayed good throwing power and ,awide bright current density range.

Grams per liter Cadmium oxide (Odo) Sodium cyanide (NaCN) .L 120 Addition agent 0.6

This bath was used for plating several objects at a current density of twenty amperes per square foot. The deposit was extremely bright and smooth. The number of grams of cadmium oxide in the above bath may be varied between fifteen and forty and good results will be obtained. If the bath be too concentrated the deposit will not be entirely satisfactory.

about three grams per The reduced, dilute solution was usedin a similar manner with similar results. About five grams per liter were used with bath (1) and liter were used with bath (2).

It is noted that less of the concentrated product was used than of the reaction mixture. The amounts used in each instance, however, represent the amount of product produced from substantially the same amounts of aldol.

The reduced amaldacets are slightly more soluble than the untreated amaldacets, and are more active as addition agents in cyanide-cad mium plating. 7

' Example XIII Following the procedure of the above Example 2H1, the reaction product of Example XI was hydrogenated. The resulting product and a concentrated product were somewhat more soluble in cyanide-cadmium baths and were effective as;

addition agents in somewhat smaller concentrations than the corresponding products of Example XI. The addition agents of this example produced results comparable to those of Example XII when used in similar baths at similar concentrations.

Example XIV The -crotoiialdehyde-monoethanolamine reaction productof Example I was dissolved in an alkali metal cyanide solution, and zinc dust was added to reduce the product. The product gave results comparable with those obtained in Example IHI when employed in similar cyanide-cadmium baths.

The other amaldacets shown above in Examples II, III, IV, V, VI, VII, VIII, and IX may'similarly be reduced to produce improved addition agents of my invention.

In the foregoing examples, zinc dust was employed as a reducing agent largely because of its convenience, but as will be evident, other refore mentioned amaldacets, such as a reduction product of theamaldacet of Example VI, are not readily soluble in cyanide-cadmium plating baths, and it is desirable that they be dispersed in the baths. With the reduction products of the amketaldoresins generally, likewise, it is expedient to disperse the addition agent if difllculty is encountered in dissolving an optimum quantity. The addition agents may be dispersed and their dissolution aided by adding them to a cyanide-cadmium bath in a suitable solvent. such as alcohol or acetone. It may sometimes be found desirable to reduce the addition agents to a finely divided state, or to use them in conjunction with such dispersing agents as saponin, gum arabic, and sulflte cellulose waste.

While my addition agents are effective in any customary cyanide bath, I prefer to use baths of the kind set forth in U. 8. Patent 1,681,509 to Mr. Leon R. Westbrook and as shown in Example XII, bath (1). These baths are of the cyanide type, and contain a small amount of a compound of a metal of the iron group having an atomic weight greater than fifty-eight. The details as to the formulation and use of these baths may be found in the said Patent 1,681,509 and need not be duplicated here.

The plating baths of the said Patent 1,681,509 are modified, as shown above, only by employing my novel addition agents in lieu of the addition agents, goulac, dextrin, starch, etc., mentioned therein. While the plating processes described in the said Patent 1,681,509 lead to a bright, hard, dense, and smooth deposit of cadmium, and while the invention therein described and claimed has been widely accepted by the art because ofits merit, the substitution of my addition agents for those in the patent results in a cadmium deposit of even greater smoothness, uniformity, and brightness.

Of course, I may use other compounds of metals of the iron group having an atomic weight greater than fifty-eight, such as nickel, copper,

etc., as disclosed in the heretofore mentioned Patent 1,681,509, but the use of cobalt compounds, as in Example XII, bath (1), has led to the best results. 1

p I desire that it be clearly understood that the whole disclosure of the heretofore mentioned Patent 1,681,509, as well as that of U. S. Patent 1,564,413 to Clayton M. Hofl, cited therein, is to be. considered, in its entirety, as an integral part of my disclosure, as my novel addition agents co act with the cyanide-metal compound baths therein to produce a result unexpected from an examination of the attributes of either of my :addition agents or the baths of the said patent,

for baths of such high concentration cannot be used to advantage withoutthe metal compounds added by Westbrook.

WhileI have discussed above the use of baths of the Westbrook type, I do not wish to be lim-; ited thereto. I'prefer to use them because. of

certain commercial considerations, and because they may be more concentrated, but excellent results are obtainable with other types of baths such as, the one shown, for instance, in Examplev The amaldacets are, of course, derived from certain aliphatic ketaldones: the aldacets; Below are discussed typical amketaldoresins derived from other aliphatic ketaldones and from carbocyclic ketaldones.

The following typical aliphatic ketaldones were tried as starting materials for the production of I amketaldo-resins which could be hydrogenated according to my invention. The aldecets are included for purposes of comparison. The. compounds in the respective lists are given in about theorder of their desirability as starting materials.

Aldehydes .-Aldol Acetaldehyde Crotonaldehyde Paraldol Propionaldehyde u-ethyl p-propyl acrolein Butyraldehyde Acrolein Citral Citronellal Hexadecoic aldehyde Isobutylaldehyde Ketones Diethyl ketone Methyl n-propyl ketone Methyl ethyl ketone Diacetyl Light acetone oil Heavy acetone oil Isobutyl ketone Acetone Iso amyl ketone Considering more specifically the preparation of amketaldoresins from the above aliphatic ketaldones, the following specific examples are given:

Example XV Example XVI Methyl ethyl ketone was treated at room temperature with gaseous ammonia. The resulting reaction product, when hydrogenated, displayedactivityas an addition agent in cyanide-cadmium plating baths.

Example XVII Five parts by weight of propionaldehyde were mixed with three parts by weight of sodium cyanide and ten parts by weight of water. The mixture was maintained at a temperature of about 50 C. for two hours and'then allowed to cool.

. XII, bath (1). 'The lower layer, when reduced,

There was a change in the appearance of the mixture during the reaction period. The reaction product was av homogeneous, mobile liquid, light yellow in color.

The addition agent of this example was reduced and used in a cyanide-cadmium bath such as that of Example XII, bath (1),,the addition agent of this example being used at a concentration of about 1.4 cc. per liter in lieu of the conand the bath was characterized by good throwing power and a relatively wide bright current density range.

Example XVIII Diethyl ketone was treated with sodium cyanide according to the procedure of Example. XVII, and the reaction-product permitted to' stand a few days. arated into two layers: a colorless lower layer, which is probably sodium cyanide solution, and an upper layer light yellow in color. While I may use both layers mixed together, I prefer to separate, and use, the upper layer;

The yellow upper layer was reduced with zinc dust and used in cyanide-cadmium baths .of the type shown in Example XII, bath (1) at an optimum concentration of 5 cc. per liter. Excellent results were obtained. The colorless lower layer, when reduced, displayed no appreciable activity as an addition agent.

Example XIX Methyl ethyl ketone was treated with sodium cyanide according to the procedure of Example XVII and. then allowed to stand a few days. The reaction mixture separated into a lower, light yellow layer, and a small upper layer, dark red in color. Again I may use the mixture, but I prefer to use the upper layer.

The upper, dark red layer was reduced. with zinc dust and used; at a concentration of 6 cc. per liter in a cyanide-cadmium bath of the type shown in Example XII, bath (1), with fair results. The lower, light yellow layer, when reduced, was not substantially effective as an addition agent in cyanide-cadmium plating.

Example XX Example XXI Methyl n-propyl ketone was treated with sodium cyanide according to the procedure of Example XIX. A colorless upper layer and a colorless lower layer were obtained. Again .I may use the reaction mixture, but I prefer to use the upper layer.

The upper layer was reduced, and was found The reaction mixture septo be a good addition agent when employed at a v concentration of 6 cc. per liter in a cyanidecadmium bath of the type shown in Example showed no substantial effect asan additionagent in cyanide-cadmium baths.

Example XXII Acetone was treated with sodium cyanide acsomewhat effective as an addition agent in a cyanide-cadmium bath of the type shown in Example XII, bath (1).. When reduced and used as an addition agent in a bath of the same type,

factory at a concentration of 18 cc. per liter.

Example XXIII B utyraldehyde was treated with sodium cyanide according to' the procedure of Example XIX.

The two layerswhich formedmay both be reduced to produce addition agents, and I may use either .or the mixture.

The lower layer, after reduction, gave good results as an addition agent at a concentration of 15 cc. per liter in a cyanide-cadmium bath of the type shown in Example XII, bath (1').

The upper layer, after reduction, produced even better results at 'a. concentration of only 5 cc. per liter in a cyanide-cadmium bath of the same type.

Example XXIV Hexadecoic aldehyde was treated with sodium cyanide according to the procedure of Example XVII, the mixture of aldehyde and cyanide being maintained at about 50 C. for four hours. Thereaction mixture was allowed to stand overnight and was found to have separated with a top layer of'nearly black cyanide reaction product. It is noted that the original aldehyde was light yellow in color.

The lower layer, "even when reduced, had no appreciable effect as an addition agent in a cyanide-cadmium bath of the type shown in Example XII, bath (1). The upper layer, after reduction, was rather diflicultly soluble, but at its optimum concentration of 5 cc. per liter, it served as' an addition agent in a cyanide-cadmium bath of the same type. The agent produced from the top layer being poorly soluble, it should be dispersed in the bath after the manner hereinbefore suggested.

When aliphatic ketaldones are used as starting materials, a ketaldone should be selected which contains at least two carbon atoms. Formaldehyde, with but one carbon atom, stands in a unique position with respect to aldehydes generally. Its dissimilarity to the other aldehydes is, of course, generally recognized.

Two hundred cubic centimeters of a forty per cent solution of formaldehyde was slowly added I to a solution of sixty grams of sodiumcyanide in eighty cubic centimeters of water. The temperature rose rapidly, and the reaction vessel was cooled to maintain a temperature of about 45 to 50 C. After about two-thirds of the formaldehyde was added, the addition of the remaining one-third produced no appreciable effect. After about ten minutes, however, the reaction'mixture became hot and it was necessary to cool it. After the reaction was complete, a dark colored product was obtained. This product was tried vas an addition agent, using from one to ten grams per liter, in a bath of the type shown in Example IUI, bath (1) and it was found that the product had only a slight effect on the character of cadmium deposit. No substantial improvement resulted from reduction of the agent;

In view of the diiference between formaldehyde and other aldehydes, one would expect formaldehyde to behave differently as a starting material for the production of addition agents. As addition agents prepared from formaldehyde are of a different order of effectiveness and are of a different character from the agents prepared from other aldehydes, I prefer to employ ketaldones which have more than one carbon atom.

1 starting materials. Hexadecoic aldehyide, for

instance, with sixteen carbon atoms led to the production of a relatively insoluble, though operative, amketaldoresin. I prefer, accordingly,

to employ aliphatic ketaldones containing between two and nine carbon atoms. This terminology includes acetaldehyde, for example, as a two carbon atom compound and citral as a nine carbon atom compound. I especially prefer to employ those aliphatic ketaldones of two to nine carbon atoms which contain no more than two hydroxyl groups.

I have found that it is not desirable that the aliphatic ketaldones contain carboxyl groups. Moreover, the elements sulfur and nitrogen are preferably absent from the aliphatic ketaldones which I employ as starting materials for the production of amketaidoresins. I especially prefer to use aliphatic ketaldones which contain only carbon, hydrogen, and oxygen, and in which the hydrogen-oxygen ratio is higher than that of water.

,While, as is noted above, I prefer that the allphatic keltaldones which I employ as starting materials contain no more than two hydroxyl groups, and,more specifically, that they have a higher ratio of hydrogen to oxygen than that of water, it is, nevertheless, within the scope of my present invention touse such ketaldones as ke toses and aldoses.

When carbohydrates which contain an aidehyde or ketone group are treated with an amo or with an alkali metal cyanide and then reduced, products similar to those above may, with some difliculty, be prepared. The reduced amketaidoresins thus produced, however, are of a different order of effectiveness than the preferred reduced amketaidoresins.

The following example illustrates the production of a reduced amketaldoresin from a-carbohydrate which contains a ketaldonyl group.

Example XXV Glucose was treated with an. alkali metal cyanide by adding 12.3 grams of glucose to a cyanide solution made by adding 3.3 grams of sodium cyanide to 10 cubic centimeters of water. The mixture was maintained at'about to C. for eighteen hours and was agitated intermittently. During the period of treatment, a faint odor of ammonia was observed.

At the end of the eighteen hours, the product was a dark red-brown, viscous liquid. This product was allowed to stand for about five hours, and then four and one-half cubic centimeters of dilute sulfuric acid was added thereto. This quantity of sulfuric acid was an excess over the amount required to react with the unreacted sodium cyanide.

When the acid was added, some heat was evolved, and there was foaming of the product.

After the foam subsided, the product was a clear,

red-brown, homogeneous liquid.

The product producedwa's reduced with zinc dust and employed as an addition agent in cyanide-cadmium baths of the type shown in Example XII in various concentrations up to ten grams per liter. The addition agent effected a considerable change in the character of the cadmium deposits, but was none too satisfactory. noted that the baths containing the addition agent were reddish-yellow in color.

For purposes of direct comparison, glucose was employed as an addition agent for cyanide-cadmium baths of the same type and in the same concentrations as were the products of this example. Glucose itself was much less effective than its reduced cyanide-reaction product. It is noted that the baths containing glucose were light-yellow in color.

The reduced amketaldoresins prepared from the aliphatic ketaldones have been discussed above in some detail, and it is now proposed to discuss briefly the preparation of reduced amketaldoresins from carbocyclic ketaldones.

The reduced amketaldoresins may be prepared by the treatment of carbocyclic ketaldones with an amo or cyanide according to procedures similar to those above discussed.

The following carbocyclic ketaldones, tried as starting materials for the production of amketaldoresins, are listedin the approximate order of their desirability. I

1. cyclohexanone 2. Methyl cyclohexanone Benzoin Benzaldehyde Anisic aldehyde Cinnamic aldehyde Quinone Vanillin Ortho-ortho dicarboxy benzoin In order more fully to describe the, production of the reduced amketaldoresins from the carbo- Example XXVI Equimolecular proportions of monoethanola mine and benzaldehyde were reacted to room temperature, and the reaction mixture reduced. The product displayed activity as an addition agent in a cyanide-cadmium plating bath of the type shown in Example XII, bath (1).

Example XXVII Example XXV'III Benzaldehyde-was treated at 50 C. for several hours with an excess of sodium cyanide solution. The cyanide solution contained three parts by weight of sodium cyanide to ten parts by weight of water. Asthe benzaldehyde was added to the cyanide solution a precipitate of some relatively insoluble material formed. ,Aft'er a few hours most of this precipitate had dissolved. The reaction mixture, after reduction, was employed quite successfully with a cyanide-cadmium bath of the type shown in Example XII, bath (1).

It is' Benzaldehyde is known to form benzoin in alkaline solution according to the following:

Accordingly, I believe that the precipitate noted above was benzoin, and that on further treatment at 50 C. some further change took place which resulted in the formation of a more soluble compound. The benzoin may have reacted with ammonia, or cyanide, condensed further, or perhaps all.

Eivample XXIX and reducing, were quite satisfactory addition agents in cyanide-cadmium baths of the type shown in Example XII, bath (1) Example XXX As the starting materials, benzaldehyde and benzoin, are diflicultly soluble, I added two carboxyl groups to benzoin thus:

COOH COOH H H o no This ortho-ortho dicarboxy benzoin was much more soluble than benzoin, but it was none too satisfactory as a starting material for the production of addition agents. Ortho-ortho dicarboxy benzoin was treated with cyanide, as in the above examples, and, after reduction, the prod-' not was found to possess some activity as addition agent in cyanide-cadmium baths.

The other carbocyclic compounds above listed may similarly be treated with an amo or cyanide according to the above procedures with good results. It is noted that instead of using methyl cyclohexanone, I may use other alkyl substituted cyclohexanones. I may, of course, use more than one allcyl substituent.

While generally I may advantageously employ any carbocyclic ketaldone, I prefer to use as starting materials ketaldones which do not contain a carboxyl group and which do not contain sulfur. Moreover, carbocyclic ketaldones which do not contain nitrogen are ordinarily preferred, because while Michlers ketone, for instance, responds to my broadest definition, it is none too satisfactory a starting material. Specifically, I prefer to employ carbocyclio ketaldones which contain only carbon, hydrogen, and oxygen and in which the hydrogen-oxygen ratio is greater than that of water.

The foregoing discussion of the aromatic ketaldones is limited to a preferred group, the carbocyclic ketaldones. It will -be understood, however, that my invention in its broad aspects includes the use of cyclic ketaldones generally. I may, for instance, use heterocyclic ketaldones as starting materials for the preparation of addition agents for cyanide-cadmium plating baths.

The following example illustrates the practice of my invention using a heterocyclic ketaldone:

Example XXXI Six and one-half grams of freshly distilled furfural was added to a sodium cyanide solution made up of 3.3 grams of sodium cyanide in 10 cubic centimeters of water. Quickly there was produced a red, heterogeneous mixture which was then maintained for six hours at 45 to 50 C. During the reaction period, a faint odor of ammonia was observed. At the end of the six hours, the mixture had reacted to form a black, tarry, lower layer and a brown, supernatant liquid. The black lower layer, after reduction, is effective as an addition agent.

The reaction mixture obtained above, before reduction, was treated with an excess of dilute sulfuric acid over that required to react with excess sodium cyanide, after the procedure of Example X. Upon the addition of acid, a violent reaction took place, and a small amount of a black, liquid tar separated from the upper layer and joined the tar already at the bottom of the reaction receptacle.

The mixture of tars was employed, after reduction, as an addition agent in cyanide-cadmium baths of the type above shown in Example XII. The baths were of a reddish color. Excellent results were obtained, but the agent of this example did not cause the baths to display as extended a bright current density range as did the agents of Example X.

The agents of this example are rather diflicultly soluble, and it is preferred to add them to cyanide-cadmium baths in a suitable solvent a dark, wine color.

such as alcohol. An optimum effect appears to be obtained when from about one-half to two grams per liter of the agents are used.

It will be understood that the conditions for the preparation of the furfural-cyanide products of this example may be widely varied. It is preferable that about an equivalent amount, or a slight excess of sodium cyanide be used. It should be noted in this connection that a great excess of cyanide is not satisfactory as, in efiect, the furfural would be present in too small a concentration for the proper reactions to take place.

Furfural was employed as an addition agent for cyanide-cadmium baths, of the type used in.

Example XII, in various amounts up to about ten grams per liter. After standing for several hours, the baths became very dark in color, and appeared black. By strong transmitted light, a small sample of one such bath appeared to have While furfural, in relatively large amounts, displayed some'activity as an addition agent, it was very much less efiective than the reduced furfural-cyanide products of this example.

I It will be understood therefore that in the production of am'ketaldoresins no such great departure fromeequimolecular proportions should be made. It will also be evident that the reacting materials should not be too dilute.

In order conveniently to merchandise my novel -addition agents, I may incorporate them with the dry ingredients employed to make up a plating bath. The resulting dry mixture can then be packaged and sold to the consumer who needs (only ,to dissolve the mixture in .water for use.

' Again, I may find it desirable to incorporate the sirable to merchandise the novel addition agents as such.

While I have disclosed a number of specific cyanide-cadmium baths heretofore, it will be understood that I do not intend to be limited thereby and that the teachings of my invention may be applied to cyanide-cadmium baths generally.

It will also be understood that I do not intend to be limited to the specific reduced amketaldoresins above disclosed, as numerous other such compositions can readily be prepared by those skilled in the art according to the principles of my invention.

I claim: A,

1. A cyanide-cadmium plating composition containing a hydrogenated amketaldoresin, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pro-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

2. A cyanide-cadmium plating composition containing a hydrogenated amketaldoresin derived from a carbocyclic ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

3. A cyanide-cadmium plating composition containing a hydrogenated amketaldoresin derived from art aliphatic ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

4. A cyanide-cadmium plating composition containing a hydrogenated amketaldoresin derived from an aliphatic ketaldone which contains only carbon, hydrogen, and oxygen, which has no less than two and no more than nine carbon atoms, and in which the ratio of hydrogen to oxygen is greater than that of water, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone withan amo in alkaline solution.

5. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an amo with an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, croto. aldehyde, and paraldol,-the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

6. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an amo with aldol, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

'7. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with a ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution. 1

8. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with a carbocyclic ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

9. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with an aliphatic ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

10. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with an aliphatic ketaldone which contains only carbon, hydrogen, and oxygen, which has no less than two and no more than nine carbon atoms, and in which the ratio of hydrogen to oxygen is greater than that of water, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

11. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with an aldacet, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product, an aldacet being, as herein set forth, one of the aldehyde equilibrium products which result when acetaldehyde is put in alkali metal cyanide solution.

12. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, crotonaldehyde, and paraldol, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

13. A cyanide-cadmium plating composition containing a hydrogenated reaction product of an alkali metal cyanide with aldol, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

14. A cyanide-cadmium plating composition containing a hydrogenated amketaldoresin and a small amount of a metal of the iron group having an atomic weight greater than fifty-eight, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pro-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

15. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising a hydrogenated amketaldoresin, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the amketaldoresin in alkaline solution, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

16. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising a hydrogenated reaction product of an alkali metal cyanide with a ketaldone, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

17. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising a hydrogenated reaction product of an alkali metal cyanide of an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, crotonaldehyde, and paraldol, the extent of hydrogenation being of the magnitude of the hydrogenation obtainable by the addition of zinc dust to the reaction product in alkaline solution.

GEORGE LUTZ. 

